Tuesday, July 17, 2007

There was no environmental impact as a result of yesterday’s automatic shut-down of three units at Japan’s Kashiwazaki Kariwa nuclear power plant following an earthquake.

The Japan Atomic Industrial Forum (JAIF) today confirmed for NucNet that units 3, 4 and 7 of the plant, in Niigata prefecture in the west of the country, shut down safely. The plant’s other units – Kashiwazaki Kariwa-1, -2, -5 and -6 – were already shut down at the time of the earthquake for periodic inspections.

At unit 6, about 1.2 cubic metres of water leaked from a system draining water to the sea, but the level of radioactivity was within the permissible limit. Inside the reactor building, a total of 1.5 litres of radioactive aqueous liquids were spilled.

At unit 3, a fire broke out in a main transformer in the non-nuclear part of the plant and was extinguished within two hours.

A JAIF spokesman said: “The cloud of black smoke that was filmed by television crews did scare some people watching television. But it was a small fire and there was no release of radioactivity or environmental impact.” No other Japanese units were affected by the quake, said the spokesman.

On Tuesday, officials said about 100 drums containing low-level nuclear waste fell over at the plant during the quake. They were found a day later, some with their lids open, said Masahide Ichikawa, an official with the local government in Niigata prefecture.

A spokesman at Tokyo Electric Power Co., which runs the plant, said the company was still trying to determine whether any hazardous material had spilled but said there was no effect outside the plant.

Definitions are important here. When you hear the term, "low-level radioactive waste" it refers to solid materials that have been exposed to radiation during normal operations of the plant. According to an article on the NEI Web site:

Low-level waste is solid material. It generally has levels of radioactivity that decay to background radioactivity levels in under 500 years. About 95 percent of the radioactivity decays to background levels within 100 years or less.

Items that become low-level waste. Low-level waste includes such items as gloves and other personal protective clothing, glass and plastic laboratory supplies, machine parts and tools, filters, wiping rags, and medical syringes that have come in contact with radioactive materials. Low-level waste from nuclear plants typically includes water purification filters and resins, tools, protective clothing, plant hardware and wastes from reactor cooling-water cleanup systems.

The Kashiwazaki-Kariwa nuclear power plant successfully withstood a major earthquake that struck northwestern Japan on July 16. The operating reactors shut down as designed. Some radioactivity was released as result of the event, but no public or environmental harm has resulted from the releases. The company still is investigating the full effects of the earthquake but has stated that there is no environmental or safety impact beyond the plant site.

BackgroundA strong earthquake that struck northwestern Japan on Monday affected operations at the seven-unit Kashiwazaki-Kariwa nuclear power plant. Four of the reactors shut down automatically, as designed (the other three were not operating at the time).

The earthquake caused approximately 300 gallons of water to spill from one reactor’s used fuel pool into an adjacent tank, from which it was then pumped to the sea. The water contained a small amount of radioactivity—about two microcuries, according to officials with Tokyo Electric Power Co. (TEPCO). The company stopped the release of the radioactive water, but not before it reached the Sea of Japan.

According to official reports, no “significant change” to the seawater has been detected near the plant. Jun Oshima, an executive at TEPCO, told the Associated Press that “the radioactivity is one-billionth the legal limit” of the water from the plant.

According to some reports, the earthquake also tipped over barrels containing low-level radioactive waste. A TEPCO spokesman said the company still was determining whether any barrels had leaked, but said it had found no effect outside of the plant.

The earthquake, estimated at 6.6-6.8 on the Richter scale, also caused a transformer fire at the facility that was quickly extinguished. The fire and the releases were not related.

Despite the considerable damage to the surrounding area, the Kashiwazaki-Kariwa nuclear plant performed as designed and withstood the effects of the earthquake. As a result, no environmental damage has resulted from the quake’s impact on the plant.

U.S. and Japanese nuclear plants are built with a “defense-in-depth” philosophy that uses multiple safety barriers and redundant, physically separated safety systems to ensure that public health and safety is assured even in severe circumstances like hurricanes and earthquakes.

18 comments:

Anonymous
said...

I saw many similar comments through other news outlets today. One made a point of mentioning that this Tokyo Electric facility was the site of Japan's worst nuclear incident. It went on to describe that 4 workers were killed by a steam leak. How is it that a steam injury that could happen at any fossil-powered plant throughout the world suddenly becomes the "worst nuclear incident in Japan"?

"How is it that a steam injury that could happen at any fossil-powered plant throughout the world suddenly becomes the "worst nuclear incident in Japan"?"

The same way the transformer fire at Kashiwazaki-Kariwa becomes a potential nuclear incident.

Remember the transformer fire at Indian Point? The same thing was going on here.

So, how is it that a steam injury that could happen at any fossil-powered plant throughout the world suddenly becomes the "worst nuclear incident in Japan"?

Here's why, courtesy of our friend Stewart Peterson:

Anything that has anything to do with anything nuclear gains super-powers, apparently, in the doctrine of Nuclear Exceptionalism that completely and totally ignores how Things Actually Work. Replacing the Physics is a system of shooting-the-messenger associations with absolutely no basis in reality.

Can anyone clear up the correspondence between the plant design basis and the actual earthquake magnitude? It's being widely reported that the quake exceeded the plant design basis. That seems possible if the quake was 6.8 on the Japanese (Omori) scale. However, if the quake was a 6.8 Richter scale event, it seems unlikely that the design basis was exceeded. Has anyone been able to sort this out?

Well according to this article from North County Times, the Kashiwazaki-Kariwa nuclear plant experienced a 6.8 quake several years ago and everything came out fine. This recent quake was supposedly measured at a 6.6 according to the article. But I'm also reading 6.8. Either way, it's survived one of these before so I'm sure it's in its DB.

The article is mostly about San Onofre in California, but the topic is on earthquake safe reactors due to recent events.

I know that everything shut down fine, but I personally would go walk down all systems important to safety to ensure that all is well, especially in the reactors currently shut down. There could be hangers / snubbers damaged, concrete cracked, valves mis-aligned, etc. These could be latent issues for future plant operations.

If my house is hit by a big earthquake and is still standing afterwards, I am still going to look it over for cracks and shifting. Survival is one thing, but future operations is another.

I've seen the radioactivity level claimed somewhere (and I can't find it) where the level was only 2 or 3 microcuries released at the Japanese nuclear plant. So anonymous possibly has it correct. ondrejch, I think you have it backwards. Top soil is more radioactive than what has been leaked so far. But this is of course off the top of my memory.

OK, we're getting more information from official sources. The earthquake was approximately the plant design basis at 6.6 to 6.8 Richter. However, seismic sensors on site measured peak ground accelerations of .31 to .68 g while the design basis acceleration may have only been about .25g. No reported damage to any safety systems but damage to non-safety systems not designed for seismic (of course). The release activity was originally reported as 1.6 microcurie and revised up to 2.4 microcurie. Insignificant in any case.

One of the key factors in looking at Richter levels is that Richter is rated at the epicenter, not at the site location. The 2004 quake was apparently slightly stronger than the 2007 quake but the epicenter was 80km away in 2004, but only 10km away in 2007. For all intents, the 2007 quake was at the site.

For the rest - I couldn't find any really quotable sources of a typical radioactivity of soil, and I am out of town so I don't have my archive with me now... Does anyone have such a reference at hand? Thanks...

Keng - do you have a quotable source of that 2.4 milicuries, please?

Our dear antinukes started a havoc again, so lets have some fun. With "Dangerous wheelbarrow of soil" greetings.

I'm trying to put two or three microcuries in perspective and I need help. I'm just a simple ex-nuclear engineer trying to understand the complex and intricate ways of the mainstream media.

Three microcuries. How many human bodies is that? If 20 people jump into a swimming pool, is this a radioactive leak into the swimming pool?

How many bananas is that? If I dump a truckload of bananas into Lake Michigan, would the New York Times report this as a "radioactive leak"? Suppose the next day, I announced that actually it was 1.5 truckloads of bananas. Would the NYT print a headline saying that I had underestimated radioactive releases by 50%?

Anon - that sort of what I was calculating. 2 microcuries are about 0.1 cubic meter of standard soil, or 4000 standard bananas (http://enochthered.blogspot.com/2007/07/bananas.html) in terms of the natural radioactivity.

Here is a calculation estimating human body radioactivity to about 8kBq, which is about .22 microcurie. So it takes 10 people to jump in the ocean to make a similar radioactive threat as the leak...

In all seriousness, I think the media coverage has been a disgrace to the profession. It's a misnomer to call the event a "radioactive leak" or release or anything of the sort, especially without putting the activity in context.

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